In substrate processing, reaction byproducts, for example formed from reactions of process gases provided to a substrate process chamber, are typically evacuated from the process chamber via an exhaust port. The exhaust port is typically disposed below a plane of the substrate being processed in the chamber on the floor or one or more sides of the process chamber. However, the inventor believes that by evacuating the reaction byproducts in such a manner, the reaction byproducts may be forced to flow across the top surface of the substrate. The inventor further believes that, as the reaction byproducts flow across the top surface of the substrate, the overall composition of process gases at various points across the substrate may be changed, thus changing the dynamics of subsequent reactions across the substrate, thereby causing process non-uniformities. The inventor also believes that this effect may be exacerbated at an edge of the substrate as the reaction by products accumulate as they flow across the substrate, thus providing a highest concentration of reaction byproducts proximate the edge of the substrate closest to the exhaust port.
Therefore, the inventor has provided an improved gas distribution apparatus for use in substrate processing apparatus.